StringReplace Help

[Cap0 0]

how would i replace a string when found second occurence?

ex:

hello there hello there hello there

would turn out to be:

hello there REPLACED there hello there

[Jos 1,358]

something like this ?:

$test = "hello there hello there hello there"
$test = StringReplace ($test, "hello", "QXQX" , 1)
$test = StringReplace ($test, "hello", "REPLACE" , 1)
$test = StringReplace ($test, "QXQX", "hello", 1)